Perhaps you ask this because the UK have revealed shortcomings in Huawei's telecom products that potentially threaten UK security. At present Chinese companies are locked out of US because of the supposed risk to security, and from the UK recent report this fear is not totally unjustified. Huawei do acknowledge the need to improve certain areas, but they are a major supplier of telecom and phone products to the UK and need to meet the highest standards.
I don't know about scared of competition but the US and other countries involve in hi-tech should respect Huawei. Its recent products have rivalled Samsung's and Apple's - no mean feat - and Huawei actual phone sales have just overtaken Apple's. The threat is there for Huawei to surpass Apple in some products and if a Chinese company can develop its technology to such a high level that the rest of the world owns its products, how will the US compete?
The reason that the United States is so scared of Huawei is that the company and its foothold in the smartphone and electronics industry is one where it could dictate how the U.S. smartphone industry will operate. Huawei is a major supplier of the equipment that makes smartphones work. This means that any smartphone that is made in the United States is certain to have some kind of Huawei technology in it. With the so called trade war that is brewing between China and the United States, Huawei and the Chinese government could raise the prices of these technologiesif the U.S. were to place huge restrictions and levies on Chinese imports. If this were to happen that would mean that the prices of smartphones in the United States would rise dramatically. The smartphone industry and market is a strong one in the U.S. so the reason that the U.S. is scared of Huawei because they are afraid that they could raise the prices of their services and products thus meaning that smartphone prices would rise and would most likely put a devestating hurt to the U.S. smartphone market.