Is it necessary to follow US-Patent Act while designing a logo for clients ?

It depends on where your client is based and where the product will be sold.
In Jordan, we designers do not follow US Patents when designing, we follow local guidelines.

NO IT NOT REALLY NECESSARY TO FOLLOW US PATENT

But if the product is being sold online does it need to comply with US standards or the owner enjoys complete rights to use the logo in their particular region / country openly ?