I suspect most politicians this will be far too long and too technical for them to bother with.
In the emails I sent I did use judicious formatting. i.e. "Prevents alternative browsers" is in bold, and "this is anti-competitive" is italic so someone scrolling through it could just read those.
How it works could be dropped or pushed to the end.
""" Dear <<WHOEVER>>,
I'm writing to inform you of a change that Google is proposing which will:
1. Reduce the ability of the security agencies to do their jobs
2. Limit the ability of ordinary citizen to access the internet
3. Lock control to big tech companies and reduce innovation in the technology sector
As a citizen of <<COUNTRY>> living and voting in <<REPLACE>> and a software engineer with X years of experience, I believe this proposal (called Web Environment Integrity or WEI), although presented as improving security and privacy, is damaging because ... """
(edit: formatting and expanded the final line)