To change width of Map Block, you can do these.
#1. First, click on Map Block
#2. Drag square icon (right icon) to right or left to increase/decrease width of Map Block
You can also use this free tool to add Map, so you have more customization when style Map Block.
#3. To change width of Map on Mobile only, use this code to Custom CSS.
@media screen and (max-width:767px) {
div.sqs-block.map-block {
max-width: 150px;
}}