There is an abundance of web hosting companies in the UK and in the US. There is nothing stopping you from hosting your site in the US. The only problem you may have is the time difference if you need support. But there is a big advantage and that is cost, if the exchange rate is good it means US hosting will be cheaper.
When it comes to choosing a web host I always look at four main areas:
1. The Disk Space allowance (usually in MB) .
2. The monthly bandwidth allowance (usually in GB).
3. The cost (don't forget to add on VAT and Domain name costs).
4. The option to upgrade your package if you need more disk space or bandwidth.
Disk Space
The Disk space is important depending on how many web pages you are creating, a good way to work out how much space you need is to take the average size of one of your web pages in K and multiply it by the number of pages you expect to have. This should give you a figure in K, then divide that figure by 1024 to give you a number in Megabytes (MB). A good size is something like 50MB disk space.
Bandwidth Allowance
This is a figure usually in Gigabytes (GB). This figure is amount of data that can be downloaded by visitors to your site in a month. This figure usually includes your POP3 Email accounts and any FTP traffic that you may have including yourself uploading your pages.
This figure can usually be worked out by the size of one of your pages multiplied by the number of visitors you expect to have in a month. Usually this is very difficult to calculate as you do not know how popular your site will be, that is why it is important to select a host that allow you to upgrade your hosting package or one that allows you to pay so much extra per MB of bandwidth exceeded.
Beware of hosting services that state 'Unlimited' bandwidth - there is usually a limit, sometimes around 2.5GB.
The Cost
Always remember to check if VAT is added on the quoted prices and check if a FREE .co.uk domain name is included or if you are going to have to pay extra for a domain or extra for a .com name.
Cost of Upgrading
As I have already mentioned check to see if you can buy more disk space or more bandwidth from your host or upgrade your package if you need to, if your site expands or becomes very popular.
Buy Cheap UK Domains
Most of my UK domains (.co.uk) are purchased through either 123-Reg or 1&1 - both easy to set up and the cheapest domain names on the market.

Buy Cheap US Domains
GoDaddy are one of the cheapest places to buy .COM domain names, don't buy them in the UK and pay extra, buy your domain names from GoDaddy.

Web Host Companies
Shown below are some Web Hosts worth taking a look at.