TBH, buying a cheap Chinese burner phone with no security relevant data on it just for traveling to the US, might be better security wise than buying an expensive Google Pixel Phone with GrapheneOS on it.
Especially now where Google, a US company and bound by its laws, that produces these devices, might (start) hand(ing) out backdoor keys to their hardware.
No no no! When you break something in Linux systems you fix it. Starting over and reinstalling everything is what you do when you mess up on Windows.