I am answering with the assumptions that
A) Bangladesh's population is as much your demo as USA
B) You eventually want to have presence in both countries
So here's some numbers- B'desh has only 7% internet penetration, but 80% of those use it at least once a day and the country is overwhelmingly a young country (under 55). If your service is youth-driven, that's a plus for sure.
As a result, web advertising through Google adwords is 79% less in Bangladesh compared to the US (http://tinyurl.com/nfqzxjc)
so that is one outstanding plus - save money, get eyeballs.
This high percentage of under-45 year olds makes social media and share-ability a big piece of your marketing (more free advertising), as well as the celebratory factor of a local person (your co-founder) having 'made it big'.
Without knowing much more about the product/service I'd say social virality and lower cost-per-click by 80% are two major points in favor of a Bangladeshi launch.
The decision is yours :), happy to have a chat with you on a call this week! We can talk about the urgency you are facing, and how you could translate the momentum from Bangladesh to the US market (short answer: depends, but can be done).
First of all, it does not matter what is the origin of co-founder or the founding team as long as you are able to speak good english and execute well.
I am assuming that you are launching your website/product targeting the US demography. It is advised to register you entity in US and also use a ISP that is based in US .
Language barrier - This is only a problem if you are raising funds , making press appearances and if you english is not at par, that could be a problem. Many people from Asian origin has this problem.
If your target market segment is US, the alternative beta markets are Canada, Australia , new zealand too. People do that too !!
Origin of a person often influences his/her thought process . The design, UX, color pallet etc needs to be thought...
Other than that I honestly do not see a reason why your would be treated differently , whether you are from Bangladesh or Bhutan !!
Moreover SIlicon Valley loved 1st generation immigrants and often attribute them to have that extra hustle factor in them..
And if you want to talk to me about technology selection, market positioning, product architecture , do feel free...I can wave off the call fee for a 30 min call if you like..
The major upside is it will be easier to prove that you have product-market fit in your own backyard, for several reasons: you know your country best, no language barrier, costs will likely be much cheaper (smaller population, lower CPCs, etc.). The main downside is you won't have the same huge upside as you would if you gained traction in the US. I would highly recommend starting in your own country if you believe that will allow you to most quickly prove that people like your product / website. This is especially the case when you need momentum ASAP. Show an up-and-to-the-right growth trajectory, even if on a relatively small scale, and use the learnings and confidence to expand into new markets (and raise money if needed).