USA electrical standards and labeling

The USA has electrical test laboratories and certification processes based on the National Electrical Code (NEC) and other national standards. Electrical equipment, appliances, devices and products are tested, evaluated and subject to on-going manufacturing production inspection for the item to be marked with the agency approval information. You may have already seen the labels for "UL Listed", "ETL listed" and many others. This 3rd party review is important for your health and safety. While there doesn't seem to be a universal requirement for a product to be listed or certified by a recognized test laboratory to national safety standards, commercial and public faculties are often required to use "UL listed or equal" materials per the bid plans. Third party certification is generally associated with consumers being confident that the product is safe for use. 

Without a third party certification, consumers really don't know  how it was assembled or its ability to safely function. 

If 3rd party testing and certification is important to you, look for listing marks or labels on the item. For instance, items on the internet will tell you things about the product but are absent information about UL or ETL listing. I have seen items described as "Designed to UL" but don't display the approved marking. 

NEC article  680.23(A)(2). Transformers and Power Supplies. Transformers and power supplies used for the supply of underwater luminaires, together with the transformer or power supply enclosure, shall be listed for swimming pool and spa use. The transformer or power supply shall incorporate either a transformer of the isolated winding type, with an ungrounded secondary that has a grounded metal barrier between the primary and secondary windings, or one that incorporates an approved system of double insulation between the primary and secondary windings.