don't rush to buy links yet!
You're trying to rank for the best type of keywords (buy [whatever]), and you also want to do it in USA which is probably the most competitive market in the world. Buying even 100 quality PBNs might not be enough to help you rank for such tough keywords.
Seriously, use the money you have to hire a good SEO consultant / auditor to do the research and audit for you to tell you what it takes to rank for those ultra tough keywords, because it might come down to churning out insane amounts of content first... or having an aged, strong domain (which takes time and good references to build), or whatever.
Start with an audit and market research first, and then you'll know if you need to buy links or focus on content, or whatever.