I am absolutely sure it is harder for the US government to get your personal data from US tech companies than it is for the Chinese government to get your data from TikTok.

So am I, but “harder” doesn’t mean “hard”.

Why would US Republicans be purchasing data from the Cambridge Analytica leak if Facebook was already handing it over?

You’re confusing government - particularly the executive power - with political parties. Republicans want to manipulate the opinions of their voter base so they can get elected and be bribed by corporations. The FBI/CIA/Whatever-other-agency want to prevent their secrets from leaking, dominate and subjugate certain groups, and control global shifts of power. They, of course, also investigate illegal activities online, but that’s probably a tertiary concern at best.

And this article was posted here the other day showing that the FBI cannot access messaging data […]

You missed the very important word “legally”. We know, however, that the FBI doesn’t give a shit about doing things legally.

But that isn’t even the only concern, we’re talking straight foreign influence as a security concern here. Yes, domestic influence is also bad, I’m against propaganda and dangerous censorship of all forms, but one is absolutely worse.

Indeed, one is worse - but I don’t believe you’re correct in which one it is. Having LIVED a period of clear PsyOps, both internal and external, as well as seen US “security” agencies meddling with my country’s government, I’ll tell you the US is currently much more dangerous.