US Madame Secretary of State Mike Pompeo went to Hungary and declared that deployments of Huawei networking equipment in Eastern Europe threatened the viability of ongoing USG "partnerships" in the region (archived). The dual threat Huawei presents to the USG and its "Five Eyes Anglophone co-conspirators is as follows:

1. Huawei equipment handling internet traffic while they would prefer Cisco equipment under their control do the same, and every piece of Huawei kit deployed denies a Cisco machine the opportunity to be racked.
2. The Five Eyes are concerned the Chinese goverment may have the same level of control over Huawei kit they have over Cisco.

Whether or not Huawei equipment is subverted to aid Chinese spies, the fact that Huawei equipment does not favor USG spies is a threat to the USG under their doctrine of total information awareness. The mere possibility of internet traffic they can't intercept and molest scares them.