Final answer:
The speaker is concerned about the kingdom's negligence, which has enabled a foreign power from France to infiltrate key ports and is ready to declare its presence openly.
Step-by-step explanation:
The speaker in the provided lines is expressing concern about negligence in the kingdom that has allowed an enemy power from France to infiltrate some of the best ports with secret preparations ("secret feet"). This enemy is on the verge of declaring itself openly ("to show their open banner"). The phrase 'scatter'd kingdom' might imply a lack of unity or preparedness that the enemy is exploiting. The key takeaway here is that the power from France has observed the kingdom's negligence and has covertly made significant inroads, poised to publicly advance its position.