If you haven’t generated any revenue then it’s gonna be hard, you should focus and work towards creating that proof of concept with your current customers, only then you can bring this to investors and entice them to look and invest into your application.
If you are not a US based companies, you can use service like Stripe Atlas or similar services to incorporate your business in US, this would make it easier for you to reach US investors, as a US based companies they are gonna be more keen to invest to your company.
You can go to sites like angel.co and there are so many other sites now that offer service to help you get introduced to investors or provide you with business loans if that is an option to you.
In other words, just grind to get to your goals, asking advice is good but do not let it deter you from reaching your main goal, if beyond reasonable doubt that your main goal is within reach then just go with it, if it’s out of reach then figure it out.
good luck.