The easiest way to find a postdoctoral position in the United States is to look at postdoctoral job offers advertised on job websites. Recruiters post their offers on these platforms and you can apply either by emailing the recruiter directly or through the website application page.
Use your network
Collaborations, conferences, social network…
Postdoctoral job offers
Advertised on the internet
Apply for postdoctoral fellowship
Become more independent with your own funding
The advantage of advertised postdoctoral positions is that funding are already available and the recruiter is now looking for candidates holding a PhD !