Thanks to Ischte, Discrepancy, and others who have pioneered, streamlined, and documented this fix.
The fix worked for me. I just stopped the service and renamed inetsrv to inetsrv.old in an administrative command prompt, then Windows Update worked successfully next time, passing the same milestones detailed by JoeTS.
I will contribute my small bit by documenting further the problem that this fix fixes.
What is the problem that this fix fixes?
During Windows Update to version 1809, while showing "Working on updates 52%" on a blue background, a popup shows error message "Windows Setup" "Windows could not configure one or more system components. To install Windows, restart the computer and then
restart the installation"

After a restart, Windows Update | View update historywill show an error code of 0xC1900101 for the failed update. Retrying as suggested will eventually fail again the same way.
Restarting after this failure, the file C:$WINDOWS.~BT\Sources\Panther\setuperr.log will contain, near its end, a summary something like
the following. To read this, you need administrative privilege. If you want to see this, and if your account has admin privilege, you can:
- Click the Windows "Start" button in lower left of screen
- Type Notepad
- Right-click on Notepad and "Run as administrator"
- Open the filename above.
2019-03-28 18:53:04, Info CSI 000001cd The queue has completed running, and AI failures have occured.
2019-03-28 18:53:04, Info CSI 000001ce ==Error Summary Start==
2019-03-28 18:53:04, Error CSI 000001cf (F) Installer: ServiceModelReg Installer
Binary Name: servicemodelregai.dll ErrorCode: 8007000d
Phase: 39 Mode: Delta
Component: NONE[gle=0x80004005]
2019-03-28 18:53:04, Error CSI 000001d0 (F) Generic Command
ErrorCode: 80004005 Executable: iissetup.exe
ExitCode: 13 Phase: 38
Mode: Install (first install) Component: Microsoft-Windows-IIS-W3SVC-GC, Culture=neutral, PublicKeyToken=31bf3856ad364e35, ProcessorArchitecture=amd64, versionScope=NonSxS[gle=0x80004005]
2019-03-28 18:53:04, Error CSI 000001d1 (F) Generic Command
ErrorCode: 80004005 Executable: iissetup.exe
ExitCode: 13 Phase: 38
Mode: Install (first install) Component: Microsoft-Windows-IIS-HttpCache, Culture=neutral, PublicKeyToken=31bf3856ad364e35, ProcessorArchitecture=amd64, versionScope=NonSxS[gle=0x80004005]
2019-03-28 18:53:04, Error CSI 000001d2 (F) Generic Command
ErrorCode: 80004005 Executable: iissetup.exe
ExitCode: 13 Phase: 38
Mode: Install (first install) Component: Microsoft-Windows-IIS-CachingBase, Culture=neutral, PublicKeyToken=31bf3856ad364e35, ProcessorArchitecture=amd64, versionScope=NonSxS[gle=0x80004005]
2019-03-28 18:53:04, Error CSI 000001d3 (F) Generic Command
ErrorCode: 80004005 Executable: iissetup.exe
ExitCode: 13 Phase: 38
Mode: Install (first install) Component: Microsoft-Windows-IIS-HttpProtocol, Culture=neutral, PublicKeyToken=31bf3856ad364e35, ProcessorArchitecture=amd64, versionScope=NonSxS[gle=0x80004005]
2019-03-28 18:53:04, Error CSI 000001d4 (F) Generic Command
ErrorCode: 80004005 Executable: iissetup.exe
ExitCode: 13 Phase: 38
Mode: Install (first install) Component: Microsoft-Windows-IIS-RequestFiltering, Culture=neutral, PublicKeyToken=31bf3856ad364e35, ProcessorArchitecture=amd64, versionScope=NonSxS[gle=0x80004005]
2019-03-28 18:53:04, Error CSI 000001d5 (F) Generic Command
ErrorCode: 80004005 Executable: iissetup.exe
ExitCode: 13 Phase: 38
Mode: Install (first install) Component: Microsoft-Windows-IIS-AnonymousAuthentication, Culture=neutral, PublicKeyToken=31bf3856ad364e35, ProcessorArchitecture=amd64, versionScope=NonSxS[gle=0x80004005]
2019-03-28 18:53:04, Error CSI 000001d6 (F) Generic Command
ErrorCode: 80004005 Executable: iissetup.exe
ExitCode: 13 Phase: 38
Mode: Install (first install) Component: Microsoft-Windows-IIS-SharedLibraries-GC, Culture=neutral, PublicKeyToken=31bf3856ad364e35, ProcessorArchitecture=amd64, versionScope=NonSxS[gle=0x80004005]
2019-03-28 18:53:04, Error CSI 000001d7 (F) Generic Command
ErrorCode: 80004005 Executable: iissetup.exe
ExitCode: 13 Phase: 38
Mode: Install (first install) Component: Microsoft-Windows-IIS-NetFxExtensibilityCommon-GC, Culture=neutral, PublicKeyToken=31bf3856ad364e35, ProcessorArchitecture=amd64, versionScope=NonSxS[gle=0x80004005]
2019-03-28 18:53:04, Info CSI 000001d8 ==Error Summary End==
2019-03-28 18:53:04, Error CSI 000001d9@2019/3/28:22:53:04.712 (F) onecore\base\wcp\componentstore\com\advancedinstallerstore.cpp(580): Error HRESULT_FROM_WIN32(ERROR_ADVANCED_INSTALLER_FAILED) originated in function Windows::COM::CComponentStore::IAdvancedInstallerAwareStore_ResolvePendingTransactions
expression: HRESULT_FROM_WIN32(14099L)